The primary aim of this proposal is to systematically examine several conceptual domains in healthy young and elderly subjects and in patients with Alzheimer's disease (AD). The overarching goal is to determine whether concepts degrade in a domain specific way in normal aging or in patients with mild or moderate AD, independent of general abstraction ability. An extensive literature in children shows that may conceptual domains develop a systematic and domain specific manner, but it is unclear whether the impairment to concepts caused by AD reflects this domain specific organization as well. Some investigators have argued that AD patients have a selective deficit in the conceptual domain of 'living cells', based primarily on studies of word meaning,. However, these findings remain controversial. To test the hypothesis of domain specific impairment, this project will compare performance of AD patients and elderly controls in three different conceptual domains: (1) living things, 92) mental states, and (3) physical properties. Since this approach can also be used to address questions related to conceptual changes with advancing age, the performance of healthy young and healthy elderly subjects will also be compared. In addition, the candidate proposes to seek training in (1) the neurobiology of aging and AD, (2) neuropsychology and the clinical assessment of patients, particularly as it pertains to aging and AD, (3) statistics, and (4) ethnical conduct of clinical research.